1. Field of the Invention
The present invention relates to a stable gelled composition containing lipophilic active agents sensitive to oxygen and/or water.
2. Description of the Background
Lipophilic active agents are known for their beneficial effects on the skin, especially upon topical application. Thus, retinol has, for a long time, been used in the treatment of acne. In addition, retinol is known to be effective in correcting damage induced either by age or by excessive intensive exposure to the sun.
Consequently, the effects of retinol on cell differentiation make it possible to envisage use thereof for effectively combating the appearance of normal and small wrinkles, skin dehydration, as well as roughness and/or stiffness of the skin. The activity of retinol in the regeneration of tissues make it an important compound in healing. A repeated application of cosmetic compositions containing retinol makes it possible to eliminate wrinkles, to smooth the skin, and to repair small cracks in the epidermis.
Due to these beneficial effects, attempts have been made for a long time to formulate retinol into cosmetically acceptable compositions, in a form stable for at least several months at room temperature.
Retinol-containing compositions which can be used in cosmetics are described, in particular, in U.S. Pat. 4,826,828 and WO-A-93/00085.
In U.S. Pat. No. 4,826,828, for example, water-in-oil emulsions containing retinol, a volatile silicone, as well as a solvent for retinol and volatile silicone are described. The preferred solvent is ethanol. It has now been demonstrated, however, that retinol is degraded in the presence of ethanol. To obtain the emulsion described therein, U.S. Pat. No. 4,826,828 describes the preparation of a solution containing retinol which is mixed at the time of use with a water-in-oil emulsion in order to avoid any degradation of the retinol. In addition, the use of antioxidant and of metal-chelating agent in the aqueous phase is indicated as being essential.
The stability of such compositions, as indicated by the owner of patent U.S. Pat. No. 826,828 on the packages of its products Bioadvance and Bioadvance 2000 described therein, does not exceed one month. Thus, the stability of retinol in this type of composition is inadequate for prolonged use. Consequently, frequent and expensive restocking is required.
In WO-A-93/00085, stabilization of retinol in cosmetic compositions, by the addition thereto of a stabilizing complex containing, in association, an antioxidant and a metal ion-chelating agent, is proposed. However, while the stability of retinol appears to be enhanced in such compositions (with 60% of the retinol remaining in the composition after three months storage at 40.degree. C.), it is nevertheless true that the relative stability of retinol is due only to the presence of a large quantity of stabilizing chelating agents and antioxidants in the composition.
Numerous efforts have been made to eliminate, or at least reduce to the greatest extent possible, such stabilizers in cosmetic compositions containing retinol, while preserving its stability of the retinol in the composition to an acceptable degree for prolonged storage and use.
Additionally, many compounds other than retinol, such as derivatives of retinol, such as 0-carotene, retinol palmitate, retinol acetate, flavonoids and polyunsaturated fatty acids, exhibit similar inadequate stability for prolonged storage and use.
Thus, a need exists for gelled compositions containing lipophilic active agents sensitive to oxygen and/or waters, which are stable for prolonged storage and use.